Electric potential measuring device using oscillating device, image forming apparatus, and electric potential measuring method

Abstract

To provide an electric potential measuring device which is useful in realizing size reduction, high sensitivity, and high reliability. The electric potential measuring device includes: an oscillating device which includes torsion springs, and an oscillating body axially supported by the springs to oscillate; and signal detecting unit which is located on a surface of the oscillating body. A capacitance between the detection electrode and a surface of an electric potential measuring object is varied by varying a distance therebetween by the oscillating device, whereby an output signal appearing on the detection electrode is detected.

1. An electric potential measuring device, comprising:
 a torsion spring; 
 an oscillating body axially supported by the torsion spring such that the oscillating body oscillates about the torsion spring; 
 a detection electrode provided on the oscillating body; 
 a driver that varies a distance between the detection electrode and an electric potential measuring object disposed facing the detection electrode by causing the oscillating body to oscillate; and 
 signal detector connected to the detection electrode for detecting an output signal 
 wherein lines of electric force from the electric potential measuring object reach the detection electrode at all times while the oscillating body is oscillating. 
 
   
   
     2. The electric potential measuring device according to  claim 1 , further comprising:
 another detection electrode provided on the oscillating body, wherein a rotational axis around which the oscillating body oscillates lies substantially between the detection electrodes, in order that output signals containing information of different phases and amplitudes appear on the detection electrodes. 
 
   
   
     3. The electric potential measuring device according to  claim 2 , wherein the signal detector performs signal detection by use of a difference between the two output signals outputted from the detection electrodes. 
   
   
     4. The electric potential measuring device according to  claim 1 , wherein a surface of the oscillating body is one of a planar surface, a convex spherical surface, a convex cylindrical surface whose generating line is parallel to an oscillation central axis, and a roof-shaped surface whose edge line is parallel to the oscillation central axis. 
   
   
     5. An image forming apparatus, comprising:
 the electric potential measuring device according to  claim 1 ; and 
 image forming means, 
 wherein a surface of the oscillating body of the electric potential measuring device is disposed facing a surface of an electric potential measuring object of the image forming means, and wherein the image forming means controls an image forming process by using the signal detection result from the electric potential measuring device. 
 
   
   
     6. An electric potential measuring device, comprising:
 a torsion spring; 
 an oscillating body axially supported by the torsion spring such that the oscillating body oscillates about the torsion spring; 
 a pair of detection electrodes provided on the oscillating body such that a rotational axis around which the oscillating body oscillates lies substantially between the detection electrodes; and 
 a driver that varies a distance between the detection electrodes and an electric potential measuring object disposed facing the detection electrodes by causing the oscillating body to oscillate, 
 wherein the oscillating body is caused to oscillate such that when one of the pair of detection electrodes moves toward the electric potential measuring object, the other one of the pair of detection electrodes moves away from the electric potential measuring object. 
 
   
   
     7. An electric potential measuring method, comprising the steps of:
 preparing an electric potential measuring device comprising an oscillating body axially supported by a torsion spring such that the oscillating body oscillates about the torsion spring, a detection electrode provided on the oscillating body, and a signal detector connected to the detection electrode for detecting an output signal; 
 arranging the electric potential measuring device such that the detection electrode faces an electric potential measuring object; 
 varying a distance between the detection electrode and the electric potential measuring object by causing the oscillating body to oscillate; and 
 detecting an output signal with the signal detector, 
 wherein lines of electric force from the electric potential measuring object reach the detection electrode at all times while the oscillating body is oscillating. 
 
   
   
     8. An electric potential measuring method, comprising the steps of:
 preparing an electric potential measuring device comprising an oscillating body axially supported by a torsion spring such that the oscillating body oscillates about the torsion spring, a pair of detection electrodes provided on the oscillating body such that a rotational axis around which the oscillating body oscillates lies substantially between the detection electrodes, and a signal detector connected to the detection electrodes for detecting an output signal; 
 arranging the electric potential measuring device such that the detection electrodes face an electric potential measuring object; 
 varying a distance between the detection electrodes and the electric potential measuring object by causing the oscillating body to oscillate such that when one of the pair of detection electrodes moves toward the electric potential measuring object, the other one of the pair of detection electrodes moves away from the electric potential measuring object; and 
 detecting an output signal with the signal detector.